This invention relates to pharmaceutical compositions. In particular, this invention relates to the use of carriers containing low molecular weight compounds that reversibly change from solid to liquid at approximately 32-37° C. in compositions for otic use.
Otic compositions designed for topical application to the external ear are typically aqueous compositions. Such compositions can be formulated as simple aqueous solutions or suspensions. Alternatively, such compositions may be formulated as an oil-in-water emulsion, such as those described in U.S. Pat. No. 5,753,269. Still another possibility for use in topical otic compositions is a polymeric ingredient. See, for example, U.S. Pat. No. 5,747,061, which describes suspension formulations of the steroid loteprednol etabonate for treating the ear, eye or nose. Gel-forming compositions and gel compositions are also used for delivering otic drugs. See, for example, U.S. Pat. No. 6,316,011, which describes certain thermal responsive hydrogels suitable for administering a pharmaceutical agent across otic membranes. See also U.S. Pat. No. 6,346,272, which describes thermo-irreversible gel vehicles that may be used to deliver otic drugs, wherein the vehicle contains a polyoxyalkylene polymer and an ionic polysaccharide and the vehicle is a liquid before administration to the body and transform, upon contact with the body, into “a semi-solid gel having a very high viscosity” (Col. 2, line 64-Col. 3, line 1). The compositions of the '272 patent may be formulated as homogeneous, polyphase systems and, in addition to the polyoxyalkylene polymer and the ionic polysaccharide, optionally contain “such additives as water insoluble high molecular weight fatty acids and alcohols, fixed oils, volatile oils and waxes, mono-, di-, and triglycerides, and synthetic, water insoluble polymers without altering the functionality of the system” (Col. 3, lines 16-21).